The present invention relates to a circuit, a programming device and a programming method.
Sensor evaluation circuits include adjustment means. After the measuring transducer has been mated with the evaluation circuit, the adjustment means are programmed by storing specific quantities, e.g., offsets, amplifications and temperature coefficients, so as to compensate for manufacturing tolerances and temperature changes in the measuring transducer with which it is mated. At the end of the production line, this data is loaded into the memory provided for this purpose via separate interfaces. Separate interfaces require expensive extra contacts on the housing of the evaluation circuit and, respectively, of the sensor element that has been mated with the evaluation circuit, and these must be protected to allow use in the field, in particular to ensure that they are properly protected against electromagnetic interference.
By contrast, the circuit, the programming device and the method according to the present invention allow straightforward adjustment of sensor evaluation circuits, in particular sensor evaluation circuits for applications in motor vehicles, to be carried out at the end of the production line, additional design elements (microcontrollers or, respectively, additional adjustment contacts) being unnecessary. Herein, it is advantageous that two-fold use is made of a line that is already present, namely the analog output. This sensor evaluation circuit, which can be adjusted in a simple manner, can be used in particular for sensors which only have an analog three-wire interface. Furthermore, the circuit according to the present invention is downwards-compatible to control units which are already present and which perform further evaluation of the output signals of sensor evaluation circuits; in the case of such control units, no changes with respect to an analog output of a three-wire interface used in straightforward manner are necessary (the three-wire interface includes a ground terminal, a supply voltage terminal and an analog output).
It is particularly advantageous that three-fold use can be made of the analog output of the sensor evaluation circuit, in that it is ensured that a memory element can be programmed, and also an external programming device can be synchronized with the adjustment means via the analog output.
It is particularly advantageous that four-fold use can be made of the analog output of the three-wire interface. This means a significant simplification of the design of the housing and printed circuit board. Furthermore, there is no need for components such as capacitors that would otherwise be necessary to prevent electromagnetic compatibility problems arising from spurious irradiation of programming connections that would otherwise also be necessary. In addition chip space can be saved, as there is no need for additional bondlouds or electrostatic shielding structures for additional programming lines that would otherwise be necessary.